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	$32.96	9.761%	$36.1772	$36.18	$36.20	$36.20
Purchase #2	$216.63	11.202%	$240.8969	$240.90	$240.90	$240.90
Purchase #3	$198.76	12.336%	$223.279	$223.28	$223.30	$223.30
Purchase #4	$147.32	4.188%	$153.4898	$153.49	$153.50	$153.50
Purchase #5	$90.58	10.326%	$99.9333	$99.93	$99.95	$99.90
Purchase #6	$158.87	5.645%	$167.8382	$167.84	$167.85	$167.80
Purchase #7	$93.60	10.251%	$103.1949	$103.19	$103.20	$103.20
7 purchase totals =	$938.72		$1,024.8093	$1,024.81	$1,024.90	$1,024.80