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	$245.44	10.530%	$271.2848	$271.28	$271.30	$271.30
Purchase #2	$49.66	10.399%	$54.8241	$54.82	$54.80	$54.80
Purchase #3	$38.65	5.831%	$40.9037	$40.90	$40.90	$40.90
Purchase #4	$208.59	3.579%	$216.0554	$216.06	$216.05	$216.10
Purchase #5	$182.36	3.820%	$189.3262	$189.33	$189.35	$189.30
Purchase #6	$160.64	9.822%	$176.4181	$176.42	$176.40	$176.40
Purchase #7	$88.75	4.480%	$92.726	$92.73	$92.75	$92.70
7 purchase totals =	$974.09		$1,041.5383	$1,041.54	$1,041.55	$1,041.50