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	$169.76	10.828%	$188.1416	$188.14	$188.15	$188.10
Purchase #2	$88.56	3.681%	$91.8199	$91.82	$91.80	$91.80
Purchase #3	$88.41	9.586%	$96.885	$96.89	$96.90	$96.90
Purchase #4	$240.44	6.438%	$255.9195	$255.92	$255.90	$255.90
Purchase #5	$186.35	7.264%	$199.8865	$199.89	$199.90	$199.90
Purchase #6	$169.43	11.541%	$188.9839	$188.98	$189.00	$189.00
Purchase #7	$162.86	4.238%	$169.762	$169.76	$169.75	$169.80
7 purchase totals =	$1,105.81		$1,191.3984	$1,191.40	$1,191.40	$1,191.40