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	$173.41	10.339%	$191.3389	$191.34	$191.35	$191.30
Purchase #2	$142.93	12.445%	$160.7176	$160.72	$160.70	$160.70
Purchase #3	$63.70	10.260%	$70.2356	$70.24	$70.25	$70.20
Purchase #4	$247.50	3.154%	$255.3062	$255.31	$255.30	$255.30
Purchase #5	$116.79	10.411%	$128.949	$128.95	$128.95	$128.90
Purchase #6	$43.66	3.144%	$45.0327	$45.03	$45.05	$45.00
Purchase #7	$191.71	9.831%	$210.557	$210.56	$210.55	$210.60
7 purchase totals =	$979.70		$1,062.1370	$1,062.15	$1,062.15	$1,062.00