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	$131.61	10.866%	$145.9107	$145.91	$145.90	$145.90
Purchase #2	$226.84	11.117%	$252.0578	$252.06	$252.05	$252.10
Purchase #3	$33.48	5.408%	$35.2906	$35.29	$35.30	$35.30
Purchase #4	$120.63	3.354%	$124.6759	$124.68	$124.70	$124.70
Purchase #5	$73.34	12.802%	$82.729	$82.73	$82.75	$82.70
Purchase #6	$78.99	5.623%	$83.4316	$83.43	$83.45	$83.40
Purchase #7	$68.92	4.799%	$72.2275	$72.23	$72.25	$72.20
7 purchase totals =	$733.81		$796.3231	$796.33	$796.40	$796.30