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	$107.83	6.305%	$114.6287	$114.63	$114.65	$114.60
Purchase #2	$152.96	4.514%	$159.8646	$159.86	$159.85	$159.90
Purchase #3	$244.69	3.415%	$253.0462	$253.05	$253.05	$253.00
Purchase #4	$73.77	5.203%	$77.6083	$77.61	$77.60	$77.60
Purchase #5	$141.63	9.571%	$155.1854	$155.19	$155.20	$155.20
Purchase #6	$99.79	11.565%	$111.3307	$111.33	$111.35	$111.30
Purchase #7	$137.36	7.412%	$147.5411	$147.54	$147.55	$147.50
7 purchase totals =	$958.03		$1,019.2050	$1,019.21	$1,019.25	$1,019.10