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	$91.25	5.552%	$96.3162	$96.32	$96.30	$96.30
Purchase #2	$209.73	12.479%	$235.9022	$235.90	$235.90	$235.90
Purchase #3	$96.39	4.318%	$100.5521	$100.55	$100.55	$100.60
Purchase #4	$224.66	5.500%	$237.0163	$237.02	$237.00	$237.00
Purchase #5	$93.94	6.432%	$99.9822	$99.98	$100.00	$100.00
Purchase #6	$131.34	8.724%	$142.7981	$142.80	$142.80	$142.80
Purchase #7	$170.61	6.573%	$181.8242	$181.82	$181.80	$181.80
7 purchase totals =	$1,017.92		$1,094.3913	$1,094.39	$1,094.35	$1,094.40