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	$53.98	4.761%	$56.55	$56.55	$56.55	$56.60
Purchase #2	$96.94	10.233%	$106.8599	$106.86	$106.85	$106.90
Purchase #3	$57.61	12.581%	$64.8579	$64.86	$64.85	$64.90
Purchase #4	$155.61	10.380%	$171.7623	$171.76	$171.75	$171.80
Purchase #5	$104.37	9.364%	$114.1432	$114.14	$114.15	$114.10
Purchase #6	$34.94	7.746%	$37.6465	$37.65	$37.65	$37.60
Purchase #7	$48.85	3.471%	$50.5456	$50.55	$50.55	$50.50
7 purchase totals =	$552.30		$602.3654	$602.37	$602.35	$602.40