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	$189.33	4.868%	$198.5466	$198.55	$198.55	$198.50
Purchase #2	$53.80	6.157%	$57.1125	$57.11	$57.10	$57.10
Purchase #3	$8.52	11.782%	$9.5238	$9.52	$9.50	$9.50
Purchase #4	$163.52	13.581%	$185.7277	$185.73	$185.75	$185.70
Purchase #5	$109.42	4.617%	$114.4719	$114.47	$114.45	$114.50
Purchase #6	$85.95	11.442%	$95.7844	$95.78	$95.80	$95.80
Purchase #7	$88.50	12.408%	$99.4811	$99.48	$99.50	$99.50
7 purchase totals =	$699.04		$760.6480	$760.64	$760.65	$760.60