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	$53.42	11.170%	$59.387	$59.39	$59.40	$59.40
Purchase #2	$101.53	4.551%	$106.1506	$106.15	$106.15	$106.20
Purchase #3	$174.76	13.488%	$198.3316	$198.33	$198.35	$198.30
Purchase #4	$103.39	5.438%	$109.0123	$109.01	$109.00	$109.00
Purchase #5	$131.28	7.660%	$141.336	$141.34	$141.35	$141.30
Purchase #6	$196.61	3.738%	$203.9593	$203.96	$203.95	$204.00
Purchase #7	$84.99	13.459%	$96.4288	$96.43	$96.45	$96.40
7 purchase totals =	$845.98		$914.6056	$914.61	$914.65	$914.60