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	$46.86	11.218%	$52.1168	$52.12	$52.10	$52.10
Purchase #2	$173.61	3.760%	$180.1377	$180.14	$180.15	$180.10
Purchase #3	$209.25	9.676%	$229.497	$229.50	$229.50	$229.50
Purchase #4	$105.41	13.307%	$119.4369	$119.44	$119.45	$119.40
Purchase #5	$90.38	11.803%	$101.0476	$101.05	$101.05	$101.00
Purchase #6	$96.73	13.848%	$110.1252	$110.13	$110.15	$110.10
Purchase #7	$249.30	12.466%	$280.3777	$280.38	$280.40	$280.40
7 purchase totals =	$971.54		$1,072.7389	$1,072.76	$1,072.80	$1,072.60