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	$122.92	3.539%	$127.2701	$127.27	$127.25	$127.30
Purchase #2	$105.28	6.550%	$112.1758	$112.18	$112.20	$112.20
Purchase #3	$131.26	8.398%	$142.2832	$142.28	$142.30	$142.30
Purchase #4	$244.86	3.490%	$253.4056	$253.41	$253.40	$253.40
Purchase #5	$205.48	6.873%	$219.6026	$219.60	$219.60	$219.60
Purchase #6	$77.93	5.297%	$82.058	$82.06	$82.05	$82.10
Purchase #7	$115.30	7.871%	$124.3753	$124.38	$124.40	$124.40
7 purchase totals =	$1,003.03		$1,061.1706	$1,061.18	$1,061.20	$1,061.30