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	$191.88	10.612%	$212.2423	$212.24	$212.25	$212.20
Purchase #2	$188.63	11.640%	$210.5865	$210.59	$210.60	$210.60
Purchase #3	$192.61	5.351%	$202.9166	$202.92	$202.90	$202.90
Purchase #4	$72.80	3.632%	$75.4441	$75.44	$75.45	$75.40
Purchase #5	$130.96	10.799%	$145.1024	$145.10	$145.10	$145.10
Purchase #6	$73.72	6.573%	$78.5656	$78.57	$78.55	$78.60
Purchase #7	$227.91	6.817%	$243.4466	$243.45	$243.45	$243.40
7 purchase totals =	$1,078.51		$1,168.3041	$1,168.31	$1,168.30	$1,168.20