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	$55.46	6.146%	$58.8686	$58.87	$58.85	$58.90
Purchase #2	$166.73	4.345%	$173.9744	$173.97	$173.95	$174.00
Purchase #3	$240.86	11.633%	$268.8792	$268.88	$268.90	$268.90
Purchase #4	$145.67	6.568%	$155.2376	$155.24	$155.25	$155.20
Purchase #5	$106.48	4.335%	$111.0959	$111.10	$111.10	$111.10
Purchase #6	$136.52	4.344%	$142.4504	$142.45	$142.45	$142.50
Purchase #7	$104.92	7.503%	$112.7921	$112.79	$112.80	$112.80
7 purchase totals =	$956.64		$1,023.2982	$1,023.30	$1,023.30	$1,023.40