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	$72.53	11.552%	$80.9087	$80.91	$80.90	$80.90
Purchase #2	$118.37	7.662%	$127.4395	$127.44	$127.45	$127.40
Purchase #3	$213.53	7.498%	$229.5405	$229.54	$229.55	$229.50
Purchase #4	$224.86	7.144%	$240.924	$240.92	$240.90	$240.90
Purchase #5	$242.90	6.640%	$259.0286	$259.03	$259.05	$259.00
Purchase #6	$72.32	11.745%	$80.814	$80.81	$80.80	$80.80
Purchase #7	$118.83	7.773%	$128.0667	$128.07	$128.05	$128.10
7 purchase totals =	$1,063.34		$1,146.7220	$1,146.72	$1,146.70	$1,146.60