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	$184.34	6.410%	$196.1562	$196.16	$196.15	$196.20
Purchase #2	$71.73	12.668%	$80.8168	$80.82	$80.80	$80.80
Purchase #3	$136.81	6.368%	$145.5221	$145.52	$145.50	$145.50
Purchase #4	$131.32	6.612%	$140.0029	$140.00	$140.00	$140.00
Purchase #5	$202.47	6.132%	$214.8855	$214.89	$214.90	$214.90
Purchase #6	$57.47	9.234%	$62.7768	$62.78	$62.80	$62.80
Purchase #7	$237.83	6.568%	$253.4507	$253.45	$253.45	$253.50
7 purchase totals =	$1,021.97		$1,093.6110	$1,093.62	$1,093.60	$1,093.70