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	$96.83	7.741%	$104.3256	$104.33	$104.35	$104.30
Purchase #2	$98.87	12.538%	$111.2663	$111.27	$111.25	$111.30
Purchase #3	$81.87	9.803%	$89.8957	$89.90	$89.90	$89.90
Purchase #4	$223.84	12.302%	$251.3768	$251.38	$251.40	$251.40
Purchase #5	$64.96	6.628%	$69.2655	$69.27	$69.25	$69.30
Purchase #6	$131.32	5.623%	$138.7041	$138.70	$138.70	$138.70
Purchase #7	$184.61	8.814%	$200.8815	$200.88	$200.90	$200.90
7 purchase totals =	$882.30		$965.7155	$965.73	$965.75	$965.80