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	$166.46	7.333%	$178.6665	$178.67	$178.65	$178.70
Purchase #2	$152.48	9.815%	$167.4459	$167.45	$167.45	$167.40
Purchase #3	$159.61	4.112%	$166.1732	$166.17	$166.15	$166.20
Purchase #4	$43.60	8.211%	$47.18	$47.18	$47.20	$47.20
Purchase #5	$130.77	11.564%	$145.8922	$145.89	$145.90	$145.90
Purchase #6	$215.73	3.280%	$222.8059	$222.81	$222.80	$222.80
Purchase #7	$124.43	7.356%	$133.5831	$133.58	$133.60	$133.60
7 purchase totals =	$993.08		$1,061.7468	$1,061.75	$1,061.75	$1,061.80