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	$168.32	10.279%	$185.6216	$185.62	$185.60	$185.60
Purchase #2	$248.77	7.419%	$267.2262	$267.23	$267.25	$267.20
Purchase #3	$240.47	11.439%	$267.9774	$267.98	$268.00	$268.00
Purchase #4	$26.77	4.815%	$28.059	$28.06	$28.05	$28.10
Purchase #5	$19.87	3.449%	$20.5553	$20.56	$20.55	$20.60
Purchase #6	$119.83	12.572%	$134.895	$134.90	$134.90	$134.90
Purchase #7	$194.36	6.406%	$206.8107	$206.81	$206.80	$206.80
7 purchase totals =	$1,018.39		$1,111.1452	$1,111.16	$1,111.15	$1,111.20