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	$98.90	3.747%	$102.6058	$102.61	$102.60	$102.60
Purchase #2	$93.29	8.178%	$100.9193	$100.92	$100.90	$100.90
Purchase #3	$84.44	5.597%	$89.1661	$89.17	$89.15	$89.20
Purchase #4	$72.92	3.443%	$75.4306	$75.43	$75.45	$75.40
Purchase #5	$173.61	6.608%	$185.0821	$185.08	$185.10	$185.10
Purchase #6	$169.63	6.534%	$180.7136	$180.71	$180.70	$180.70
Purchase #7	$100.56	10.179%	$110.796	$110.80	$110.80	$110.80
7 purchase totals =	$793.35		$844.7135	$844.72	$844.70	$844.70