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	$60.31	8.550%	$65.4665	$65.47	$65.45	$65.50
Purchase #2	$59.34	4.280%	$61.8798	$61.88	$61.90	$61.90
Purchase #3	$181.58	10.450%	$200.5551	$200.56	$200.55	$200.60
Purchase #4	$182.26	11.734%	$203.6464	$203.65	$203.65	$203.60
Purchase #5	$249.57	11.531%	$278.3479	$278.35	$278.35	$278.30
Purchase #6	$34.60	4.222%	$36.0608	$36.06	$36.05	$36.10
Purchase #7	$219.52	4.598%	$229.6135	$229.61	$229.60	$229.60
7 purchase totals =	$987.18		$1,075.5700	$1,075.58	$1,075.55	$1,075.60