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	$34.57	9.507%	$37.8566	$37.86	$37.85	$37.90
Purchase #2	$144.29	12.387%	$162.1632	$162.16	$162.15	$162.20
Purchase #3	$245.26	10.205%	$270.2888	$270.29	$270.30	$270.30
Purchase #4	$133.69	6.323%	$142.1432	$142.14	$142.15	$142.10
Purchase #5	$104.27	6.298%	$110.8369	$110.84	$110.85	$110.80
Purchase #6	$130.38	13.329%	$147.7584	$147.76	$147.75	$147.80
Purchase #7	$222.58	10.137%	$245.1429	$245.14	$245.15	$245.10
7 purchase totals =	$1,015.04		$1,116.1900	$1,116.19	$1,116.20	$1,116.20