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	$209.38	3.642%	$217.0056	$217.01	$217.00	$217.00
Purchase #2	$31.64	7.133%	$33.8969	$33.90	$33.90	$33.90
Purchase #3	$171.76	11.517%	$191.5416	$191.54	$191.55	$191.50
Purchase #4	$96.28	3.318%	$99.4746	$99.47	$99.45	$99.50
Purchase #5	$23.31	7.379%	$25.03	$25.03	$25.05	$25.00
Purchase #6	$240.53	9.468%	$263.3034	$263.30	$263.30	$263.30
Purchase #7	$165.99	13.308%	$188.0799	$188.08	$188.10	$188.10
7 purchase totals =	$938.89		$1,018.3320	$1,018.33	$1,018.35	$1,018.30