Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.37	13.771%	$103.9526	$103.95	$103.95	$104.00
Purchase #2	$100.85	3.213%	$104.0903	$104.09	$104.10	$104.10
Purchase #3	$104.72	4.844%	$109.7926	$109.79	$109.80	$109.80
Purchase #4	$222.76	12.465%	$250.527	$250.53	$250.55	$250.50
Purchase #5	$152.82	10.336%	$168.6155	$168.62	$168.60	$168.60
Purchase #6	$183.52	9.799%	$201.5031	$201.50	$201.50	$201.50
Purchase #7	$189.68	11.296%	$211.1063	$211.11	$211.10	$211.10
7 purchase totals =	$1,045.72		$1,149.5874	$1,149.59	$1,149.60	$1,149.60