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	$127.69	11.310%	$142.1317	$142.13	$142.15	$142.10
Purchase #2	$141.33	10.459%	$156.1117	$156.11	$156.10	$156.10
Purchase #3	$170.65	9.751%	$187.2901	$187.29	$187.30	$187.30
Purchase #4	$91.56	8.405%	$99.2556	$99.26	$99.25	$99.30
Purchase #5	$84.80	11.375%	$94.446	$94.45	$94.45	$94.40
Purchase #6	$87.91	9.780%	$96.5076	$96.51	$96.50	$96.50
Purchase #7	$67.98	7.346%	$72.9738	$72.97	$72.95	$73.00
7 purchase totals =	$771.92		$848.7165	$848.72	$848.70	$848.70