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	$35.76	4.500%	$37.3692	$37.37	$37.35	$37.40
Purchase #2	$25.74	9.318%	$28.1385	$28.14	$28.15	$28.10
Purchase #3	$110.70	12.798%	$124.8674	$124.87	$124.85	$124.90
Purchase #4	$73.34	7.550%	$78.8772	$78.88	$78.90	$78.90
Purchase #5	$15.46	11.595%	$17.2526	$17.25	$17.25	$17.30
Purchase #6	$113.85	10.288%	$125.5629	$125.56	$125.55	$125.60
Purchase #7	$51.64	3.391%	$53.3911	$53.39	$53.40	$53.40
7 purchase totals =	$426.49		$465.4589	$465.46	$465.45	$465.60