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	$218.89	6.488%	$233.0916	$233.09	$233.10	$233.10
Purchase #2	$56.44	9.574%	$61.8436	$61.84	$61.85	$61.80
Purchase #3	$185.78	13.250%	$210.3959	$210.40	$210.40	$210.40
Purchase #4	$14.35	9.851%	$15.7636	$15.76	$15.75	$15.80
Purchase #5	$221.43	10.776%	$245.2913	$245.29	$245.30	$245.30
Purchase #6	$79.97	4.206%	$83.3335	$83.33	$83.35	$83.30
Purchase #7	$156.42	8.521%	$169.7485	$169.75	$169.75	$169.70
7 purchase totals =	$933.28		$1,019.4680	$1,019.46	$1,019.50	$1,019.40