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	$164.73	12.722%	$185.687	$185.69	$185.70	$185.70
Purchase #2	$221.54	11.514%	$247.0481	$247.05	$247.05	$247.00
Purchase #3	$114.81	11.806%	$128.3645	$128.36	$128.35	$128.40
Purchase #4	$31.81	3.243%	$32.8416	$32.84	$32.85	$32.80
Purchase #5	$150.90	6.221%	$160.2875	$160.29	$160.30	$160.30
Purchase #6	$210.61	6.469%	$224.2344	$224.23	$224.25	$224.20
Purchase #7	$198.39	4.223%	$206.768	$206.77	$206.75	$206.80
7 purchase totals =	$1,092.79		$1,185.2311	$1,185.23	$1,185.25	$1,185.20