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	$233.94	12.449%	$263.0632	$263.06	$263.05	$263.10
Purchase #2	$191.27	6.511%	$203.7236	$203.72	$203.70	$203.70
Purchase #3	$227.39	4.206%	$236.954	$236.95	$236.95	$237.00
Purchase #4	$109.83	12.371%	$123.4171	$123.42	$123.40	$123.40
Purchase #5	$142.30	9.596%	$155.9551	$155.96	$155.95	$156.00
Purchase #6	$71.25	4.543%	$74.4869	$74.49	$74.50	$74.50
Purchase #7	$40.99	3.758%	$42.5304	$42.53	$42.55	$42.50
7 purchase totals =	$1,016.97		$1,100.1303	$1,100.13	$1,100.10	$1,100.20