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	$50.99	9.640%	$55.9054	$55.91	$55.90	$55.90
Purchase #2	$191.55	10.318%	$211.3141	$211.31	$211.30	$211.30
Purchase #3	$151.80	10.461%	$167.6798	$167.68	$167.70	$167.70
Purchase #4	$232.44	10.210%	$256.1721	$256.17	$256.15	$256.20
Purchase #5	$240.82	11.498%	$268.5095	$268.51	$268.50	$268.50
Purchase #6	$76.59	7.532%	$82.3588	$82.36	$82.35	$82.40
Purchase #7	$245.57	5.383%	$258.789	$258.79	$258.80	$258.80
7 purchase totals =	$1,189.76		$1,300.7287	$1,300.73	$1,300.70	$1,300.80