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	$167.64	10.608%	$185.4233	$185.42	$185.40	$185.40
Purchase #2	$64.30	13.276%	$72.8365	$72.84	$72.85	$72.80
Purchase #3	$104.64	4.563%	$109.4147	$109.41	$109.40	$109.40
Purchase #4	$79.68	8.201%	$86.2146	$86.21	$86.20	$86.20
Purchase #5	$181.43	10.541%	$200.5545	$200.55	$200.55	$200.60
Purchase #6	$154.29	9.412%	$168.8118	$168.81	$168.80	$168.80
Purchase #7	$208.75	10.122%	$229.8797	$229.88	$229.90	$229.90
7 purchase totals =	$960.73		$1,053.1351	$1,053.12	$1,053.10	$1,053.10