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	$185.53	3.223%	$191.5096	$191.51	$191.50	$191.50
Purchase #2	$229.84	7.454%	$246.9723	$246.97	$246.95	$247.00
Purchase #3	$138.65	12.810%	$156.4111	$156.41	$156.40	$156.40
Purchase #4	$138.29	10.156%	$152.3347	$152.33	$152.35	$152.30
Purchase #5	$110.31	8.688%	$119.8937	$119.89	$119.90	$119.90
Purchase #6	$85.85	12.278%	$96.3907	$96.39	$96.40	$96.40
Purchase #7	$54.42	7.767%	$58.6468	$58.65	$58.65	$58.60
7 purchase totals =	$942.89		$1,022.1589	$1,022.15	$1,022.15	$1,022.10