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	$62.69	11.729%	$70.0429	$70.04	$70.05	$70.00
Purchase #2	$169.34	9.232%	$184.9735	$184.97	$184.95	$185.00
Purchase #3	$162.71	10.254%	$179.3943	$179.39	$179.40	$179.40
Purchase #4	$130.90	4.148%	$136.3297	$136.33	$136.35	$136.30
Purchase #5	$231.98	9.745%	$254.5865	$254.59	$254.60	$254.60
Purchase #6	$72.71	13.112%	$82.2437	$82.24	$82.25	$82.20
Purchase #7	$206.50	4.373%	$215.5302	$215.53	$215.55	$215.50
7 purchase totals =	$1,036.83		$1,123.1008	$1,123.09	$1,123.15	$1,123.00