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	$125.35	11.823%	$140.1701	$140.17	$140.15	$140.20
Purchase #2	$168.90	11.846%	$188.9079	$188.91	$188.90	$188.90
Purchase #3	$164.69	6.171%	$174.853	$174.85	$174.85	$174.90
Purchase #4	$74.76	3.247%	$77.1875	$77.19	$77.20	$77.20
Purchase #5	$182.59	7.405%	$196.1108	$196.11	$196.10	$196.10
Purchase #6	$31.32	13.300%	$35.4856	$35.49	$35.50	$35.50
Purchase #7	$73.61	8.272%	$79.699	$79.70	$79.70	$79.70
7 purchase totals =	$821.22		$892.4139	$892.42	$892.40	$892.50