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	$110.46	7.150%	$118.3579	$118.36	$118.35	$118.40
Purchase #2	$185.33	13.284%	$209.9492	$209.95	$209.95	$209.90
Purchase #3	$35.42	8.132%	$38.3004	$38.30	$38.30	$38.30
Purchase #4	$71.38	9.674%	$78.2853	$78.29	$78.30	$78.30
Purchase #5	$164.67	4.224%	$171.6257	$171.63	$171.65	$171.60
Purchase #6	$242.36	4.722%	$253.8042	$253.80	$253.80	$253.80
Purchase #7	$159.44	13.853%	$181.5272	$181.53	$181.55	$181.50
7 purchase totals =	$969.06		$1,051.8499	$1,051.86	$1,051.90	$1,051.80