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	$54.52	13.507%	$61.884	$61.88	$61.90	$61.90
Purchase #2	$62.36	8.395%	$67.5951	$67.60	$67.60	$67.60
Purchase #3	$247.48	8.690%	$268.986	$268.99	$269.00	$269.00
Purchase #4	$205.84	9.686%	$225.7777	$225.78	$225.80	$225.80
Purchase #5	$155.48	7.328%	$166.8736	$166.87	$166.85	$166.90
Purchase #6	$197.63	6.673%	$210.8178	$210.82	$210.80	$210.80
Purchase #7	$129.61	11.764%	$144.8573	$144.86	$144.85	$144.90
7 purchase totals =	$1,052.92		$1,146.7915	$1,146.80	$1,146.80	$1,146.90