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	$147.56	7.356%	$158.4145	$158.41	$158.40	$158.40
Purchase #2	$50.63	5.490%	$53.4096	$53.41	$53.40	$53.40
Purchase #3	$245.93	7.592%	$264.601	$264.60	$264.60	$264.60
Purchase #4	$220.78	8.732%	$240.0585	$240.06	$240.05	$240.10
Purchase #5	$61.85	9.229%	$67.5581	$67.56	$67.55	$67.60
Purchase #6	$246.56	9.247%	$269.3594	$269.36	$269.35	$269.40
Purchase #7	$103.66	7.806%	$111.7517	$111.75	$111.75	$111.80
7 purchase totals =	$1,076.97		$1,165.1528	$1,165.15	$1,165.10	$1,165.30