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	$89.44	11.143%	$99.4063	$99.41	$99.40	$99.40
Purchase #2	$125.38	6.842%	$133.9585	$133.96	$133.95	$134.00
Purchase #3	$33.90	4.434%	$35.4031	$35.40	$35.40	$35.40
Purchase #4	$215.32	11.349%	$239.7567	$239.76	$239.75	$239.80
Purchase #5	$189.98	11.127%	$211.1191	$211.12	$211.10	$211.10
Purchase #6	$165.74	11.473%	$184.7554	$184.76	$184.75	$184.80
Purchase #7	$196.50	13.332%	$222.6974	$222.70	$222.70	$222.70
7 purchase totals =	$1,016.26		$1,127.0965	$1,127.11	$1,127.05	$1,127.20