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	$191.44	10.288%	$211.1353	$211.14	$211.15	$211.10
Purchase #2	$173.97	12.379%	$195.5057	$195.51	$195.50	$195.50
Purchase #3	$103.87	6.460%	$110.58	$110.58	$110.60	$110.60
Purchase #4	$210.92	6.152%	$223.8958	$223.90	$223.90	$223.90
Purchase #5	$249.77	7.460%	$268.4028	$268.40	$268.40	$268.40
Purchase #6	$69.42	13.148%	$78.5473	$78.55	$78.55	$78.50
Purchase #7	$80.31	4.334%	$83.7906	$83.79	$83.80	$83.80
7 purchase totals =	$1,079.70		$1,171.8575	$1,171.87	$1,171.90	$1,171.80