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	$229.33	3.622%	$237.6363	$237.64	$237.65	$237.60
Purchase #2	$79.35	5.304%	$83.5587	$83.56	$83.55	$83.60
Purchase #3	$38.72	5.178%	$40.7249	$40.72	$40.70	$40.70
Purchase #4	$67.30	6.818%	$71.8885	$71.89	$71.90	$71.90
Purchase #5	$86.84	11.255%	$96.6138	$96.61	$96.60	$96.60
Purchase #6	$154.46	9.740%	$169.5044	$169.50	$169.50	$169.50
Purchase #7	$188.28	5.427%	$198.498	$198.50	$198.50	$198.50
7 purchase totals =	$844.28		$898.4246	$898.42	$898.40	$898.40