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	$127.81	10.403%	$141.1061	$141.11	$141.10	$141.10
Purchase #2	$185.79	11.354%	$206.8846	$206.88	$206.90	$206.90
Purchase #3	$165.72	11.110%	$184.1315	$184.13	$184.15	$184.10
Purchase #4	$39.44	7.356%	$42.3412	$42.34	$42.35	$42.30
Purchase #5	$68.52	3.345%	$70.812	$70.81	$70.80	$70.80
Purchase #6	$228.30	7.408%	$245.2125	$245.21	$245.20	$245.20
Purchase #7	$46.25	11.415%	$51.5294	$51.53	$51.55	$51.50
7 purchase totals =	$861.83		$942.0173	$942.01	$942.05	$941.90