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	$42.70	6.854%	$45.6267	$45.63	$45.65	$45.60
Purchase #2	$90.46	13.249%	$102.445	$102.45	$102.45	$102.40
Purchase #3	$69.96	11.572%	$78.0558	$78.06	$78.05	$78.10
Purchase #4	$235.73	3.435%	$243.8273	$243.83	$243.85	$243.80
Purchase #5	$223.32	9.287%	$244.0597	$244.06	$244.05	$244.10
Purchase #6	$114.78	11.250%	$127.6928	$127.69	$127.70	$127.70
Purchase #7	$219.48	10.366%	$242.2313	$242.23	$242.25	$242.20
7 purchase totals =	$996.43		$1,083.9386	$1,083.95	$1,084.00	$1,083.90