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	$144.26	7.125%	$154.5385	$154.54	$154.55	$154.50
Purchase #2	$48.83	13.826%	$55.5812	$55.58	$55.60	$55.60
Purchase #3	$182.27	4.550%	$190.5633	$190.56	$190.55	$190.60
Purchase #4	$249.69	11.482%	$278.3594	$278.36	$278.35	$278.40
Purchase #5	$57.56	11.400%	$64.1218	$64.12	$64.10	$64.10
Purchase #6	$101.77	3.704%	$105.5396	$105.54	$105.55	$105.50
Purchase #7	$61.60	6.470%	$65.5855	$65.59	$65.60	$65.60
7 purchase totals =	$845.98		$914.2893	$914.29	$914.30	$914.30