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	$169.76	7.780%	$182.9673	$182.97	$182.95	$183.00
Purchase #2	$217.72	9.463%	$238.3228	$238.32	$238.30	$238.30
Purchase #3	$75.30	5.728%	$79.6132	$79.61	$79.60	$79.60
Purchase #4	$178.91	3.466%	$185.111	$185.11	$185.10	$185.10
Purchase #5	$7.79	12.392%	$8.7553	$8.76	$8.75	$8.80
Purchase #6	$152.51	12.437%	$171.4777	$171.48	$171.50	$171.50
Purchase #7	$88.66	13.459%	$100.5927	$100.59	$100.60	$100.60
7 purchase totals =	$890.65		$966.8400	$966.84	$966.80	$966.90