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	$146.92	8.130%	$158.8646	$158.86	$158.85	$158.90
Purchase #2	$181.66	8.281%	$196.7033	$196.70	$196.70	$196.70
Purchase #3	$101.53	5.835%	$107.4543	$107.45	$107.45	$107.50
Purchase #4	$73.70	7.854%	$79.4884	$79.49	$79.50	$79.50
Purchase #5	$239.96	10.243%	$264.5391	$264.54	$264.55	$264.50
Purchase #6	$62.27	5.835%	$65.9035	$65.90	$65.90	$65.90
Purchase #7	$142.80	3.445%	$147.7195	$147.72	$147.70	$147.70
7 purchase totals =	$948.84		$1,020.6727	$1,020.66	$1,020.65	$1,020.70