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	$203.88	4.508%	$213.0709	$213.07	$213.05	$213.10
Purchase #2	$89.61	10.788%	$99.2771	$99.28	$99.30	$99.30
Purchase #3	$176.42	11.535%	$196.77	$196.77	$196.75	$196.80
Purchase #4	$240.86	3.725%	$249.832	$249.83	$249.85	$249.80
Purchase #5	$30.76	9.355%	$33.6376	$33.64	$33.65	$33.60
Purchase #6	$219.46	11.763%	$245.2751	$245.28	$245.30	$245.30
Purchase #7	$19.73	12.841%	$22.2635	$22.26	$22.25	$22.30
7 purchase totals =	$980.72		$1,060.1262	$1,060.13	$1,060.15	$1,060.20