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	$32.99	11.681%	$36.8436	$36.84	$36.85	$36.80
Purchase #2	$74.54	11.109%	$82.8206	$82.82	$82.80	$82.80
Purchase #3	$148.31	9.320%	$162.1325	$162.13	$162.15	$162.10
Purchase #4	$184.77	13.740%	$210.1574	$210.16	$210.15	$210.20
Purchase #5	$167.57	6.588%	$178.6095	$178.61	$178.60	$178.60
Purchase #6	$152.71	3.839%	$158.5725	$158.57	$158.55	$158.60
Purchase #7	$175.30	12.300%	$196.8619	$196.86	$196.85	$196.90
7 purchase totals =	$936.19		$1,025.9980	$1,025.99	$1,025.95	$1,026.00