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	$134.38	10.383%	$148.3327	$148.33	$148.35	$148.30
Purchase #2	$219.93	13.237%	$249.0421	$249.04	$249.05	$249.00
Purchase #3	$223.96	5.133%	$235.4559	$235.46	$235.45	$235.50
Purchase #4	$233.50	9.171%	$254.9143	$254.91	$254.90	$254.90
Purchase #5	$38.93	8.696%	$42.3154	$42.32	$42.30	$42.30
Purchase #6	$64.67	8.615%	$70.2413	$70.24	$70.25	$70.20
Purchase #7	$51.80	5.659%	$54.7314	$54.73	$54.75	$54.70
7 purchase totals =	$967.17		$1,055.0331	$1,055.03	$1,055.05	$1,054.90