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	$194.77	10.658%	$215.5286	$215.53	$215.55	$215.50
Purchase #2	$190.41	12.347%	$213.9199	$213.92	$213.90	$213.90
Purchase #3	$60.77	10.415%	$67.0992	$67.10	$67.10	$67.10
Purchase #4	$115.56	11.196%	$128.4981	$128.50	$128.50	$128.50
Purchase #5	$131.27	10.804%	$145.4524	$145.45	$145.45	$145.50
Purchase #6	$133.85	11.405%	$149.1156	$149.12	$149.10	$149.10
Purchase #7	$228.88	13.653%	$260.129	$260.13	$260.15	$260.10
7 purchase totals =	$1,055.51		$1,179.7428	$1,179.75	$1,179.75	$1,179.70