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	$100.59	11.524%	$112.182	$112.18	$112.20	$112.20
Purchase #2	$149.73	7.157%	$160.4462	$160.45	$160.45	$160.40
Purchase #3	$219.43	11.673%	$245.0441	$245.04	$245.05	$245.00
Purchase #4	$102.57	3.647%	$106.3107	$106.31	$106.30	$106.30
Purchase #5	$50.57	13.633%	$57.4642	$57.46	$57.45	$57.50
Purchase #6	$116.79	8.850%	$127.1259	$127.13	$127.15	$127.10
Purchase #7	$174.83	6.259%	$185.7726	$185.77	$185.75	$185.80
7 purchase totals =	$914.51		$994.3457	$994.34	$994.35	$994.30