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	$78.77	13.750%	$89.6009	$89.60	$89.60	$89.60
Purchase #2	$35.39	6.279%	$37.6121	$37.61	$37.60	$37.60
Purchase #3	$184.37	7.355%	$197.9304	$197.93	$197.95	$197.90
Purchase #4	$181.56	5.617%	$191.7582	$191.76	$191.75	$191.80
Purchase #5	$61.90	9.349%	$67.687	$67.69	$67.70	$67.70
Purchase #6	$230.42	9.278%	$251.7984	$251.80	$251.80	$251.80
Purchase #7	$186.77	6.295%	$198.5272	$198.53	$198.55	$198.50
7 purchase totals =	$959.18		$1,034.9142	$1,034.92	$1,034.95	$1,034.90